Method and apparatus for providing zoned communications

ABSTRACT

A user headset is provided that is operable to contain an audio device (50) and a receiver (52). The receiver (52) is operable to receive both audio information on multiple channels and also data. The data is received in the form of pulse width modulated sync signals. The sync signals are operable to provide a synchronization signal for 3-D liquid crystal lenses (60). The data is encoded within the sync signal through pulse width modulation. The width of the pulse defines various commands. These various commands define the channel over which the audio is to be transmitted. These channels can either be user-defined or they can be a function of the transmitter. The transmitter includes an audio generator (42) for generating audio signals on multiple channels and also a data generator (40). These are modulated onto a broad band optical signal and transmitted via an IR data link. The system facilitates a walking tour by transmitting commands to the receiver that allow the receiver to lock onto a particular channel, there being select channels for a given zone. When walking from one zone to another zone, different channels in the next zone are automatically detected. The system detects the crossing of a boundary between zones by a change in sync frequency. Since the sync signals for both zones are synchronized, this facilitates a seamless transfer between adjacent zones.

TECHNICAL FIELD OF THE INVENTION

The present invention pertains in general to communication systems and,more particularly, to a communication system for allowing a remotereceiver to traverse various zones with different informationtransmitted in each zone, with the receiver switching to the transmitterin the resident zone.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to co-pending U.S. patent application Ser.No. 08/738,227, filed Oct. 25, 1996, (Atty. Dkt. No. OXMO-23,614),entitled "Method and Apparatus for Synchronizing and Controlling RemoteReceiver," and to co-pending U.S. patent application Ser. No.08/738,220, filed Oct. 25, 1996, (Atty. Dkt. No. OXMO-23,616), entitled"Method and Apparatus for Controlling Program Start/Stop Operations,"both applications filed on even date herewith.

BACKGROUND OF THE INVENTION

In trade shows, museums, theme parks, video games, and many otherattractions, multiple displays are typically utilized for multipleexhibits or even for a single exhibit. This is also the case with somesingle entity shows, wherein multiple exhibits are contained in one halland a viewer is allowed to roam from exhibit to exhibit.

With some trade shows and with some exhibits, a user is provided a taperecorder. These type of situations are referred to as "walking tours".In a walking tour, the user is provided with the tape recorder and isinstructed to turn the tape recorder on and go to the defined exhibitnumber. At the end of the description of that exhibit, the user isinstructed to turn off the tape recorder until they go to the nextexhibit. At the next exhibit, the tape recorder is again turned on andthe narrative continued.

In another type of system, some type of receiver could be utilized withseparate transmitters disposed at each location. When a user comeswithin a particular transmit range of a given transmitter, theinformation is received. One disadvantage to this type of system is thatwith respect to "overlap", wherein two transmitters of the samefrequency are transmitting in overlapping areas. If this occurs, thereis a strong possibility that there will be some interference orincorrect signal reception. If more than one audio or data channel isprovided with any receiver, this typically will require two or moreseparate RF channels. Further, there must be some method provided bywhich channels can be changed when going into a particular zone.

SUMMARY OF THE INVENTION

The present invention disclosed and claimed herein comprises a methodfor communicating with mobile receivers in different zones. Firstprogram information is transmitted in a first zone on first programchannels from a first transmitter located in the first zone. Similarly,second program information is transmitted in a second zone on secondprogram channels over a second communication link from a secondtransmitter located in the second zone. A common command link isprovided for both of the first and second transmitters to the mobilereceiver which extends from the first and second transmitters withineach of the zones and is originated at each of the first and secondtransmitters. The common command link is used in the first zone fortransmission of first command information within the first zone andcontaining configuration information related to the first programinformation and priority information, with the first transmitter havingthe highest priority. In the second zone, the common command link isutilized to transmit second command information within the second zonecontaining configuration information related to the second programinformation and priority information, with the second transmitter havinglower priority than the first transmitter. Command information isreceived over the common command link from the one of the transmittersin whose zone the mobile receiver resides. The mobile receiver thenconfigures itself in accordance with the highest priority one of thefirst or second command signals received over the common command link.The mobile receiver is then configured to receive either the firstprogram information over the first program channel or the second programinformation over the second program channel, depending upon the highestpriority received one of the command information.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and theadvantages thereof, reference is now made to the following descriptiontaken in conjunction with the accompanying Drawings in which:

FIG. 1 illustrates a top view of a multiple zone system with threetransmitters;

FIG. 2 illustrates a diagrammatic view of the multi-zone system of FIG.1;

FIG. 3 illustrates a block diagram of the receiver/transmitter;

FIG. 4 illustrates a block diagram of the timing diagram illustratingthe synchronization and pulse with modulation technique;

FIG. 5 illustrates a block diagram of the headset;

FIG. 6 illustrates a schematic diagram of the sync detector;

FIG. 7a-7f illustrate a logic diagram of the sync pulse receiver;

FIG. 7g illustrates a timing diagram for the lens driver;

FIG. 8 illustrates a schematic diagram of one audio channel;

FIGS. 9a and 9b illustrate a schematic block diagram of the audio/syncreceiver control function:

FIGS. 10a and 10b illustrate flowcharts depicting the overall operationof the receivers;

FIG. 11a and 11b illustrate flowcharts depicting the detailed operationof the audio only mode;

FIG. 12 illustrates a diagrammatic view of the staggered audio onlymode;

FIG. 13 illustrates a flowchart for the transmitter operation in thestaggered mode;

FIG. 14 illustrates a block diagram of the receiver and transmitterdepicting an alternate embodiment;

FIGS. 15a and 15b illustrate block diagrams of the system transmitter;and

FIG. 16 illustrates a block diagram of an alternate configuration forthe transmitters and zones.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIG. 1, there is illustrated a top view of a multi-zonesystem operating in accordance with the present invention. There areillustrated three transmitters 10, 12 and 14, disposed on three separatewalls 16, 18 and 20, respectively. These walls are illustrated as beingassociated with three separate zones, Zone 1, Zone 2 and Zone 3 labeledZ1, Z2 and Z3. The Zones Z1, Z2 and Z3 are illustrated in phantom line.The transmitters 10-14 are all associated with a transmitter control 22,which transmitter control can be centralized or it can be distributed.However, there is always a common synchronization with respect to allthree transmitters 10-14, as will be described in more detailhereinbelow. In each of the Zones Z1-Z3, there are disposed multiplelisteners. For example, in Zone Z3 there are two listeners 24 and 26,which are exclusively within Zone 3 and not within Zone Z1 or Zone Z2.Zone Z2 overlaps with Zone Z3 in an area 28. In this area, there is alistener 30 traversing from Zone Z3 to Zone Z2. As such, the listener 30receives signals from both transmitter 12 and transmitter 14. With thepresent invention, the listener 30 will automatically receiveinformation from the highest priority one of the transmitters 12 or 14.Additionally, as will be described hereinbelow, this is a seamlesstransition. In a walking tour scenario, a listener could traverse froman area outside of any of the Zones Z1-Z3 and into Zone Z3. Outside ofZone Z3, the listener would not receive anything on a headset that thelistener is wearing. As soon as the listener entered Zone Z3, it wouldsynchronize to transmitter 14 and receive information and commands fromthe transmitter 14. When the user traversed from Zone Z3 to Z2, as soonas it entered the overlap region 28, Zone Z2 would take over, Zone Z2being higher priority than Zone Z3. The listener would then receiveinformation and commands from transmitter 12. Upon traversing from ZoneZ2 to Zone Z1, the listener would traverse an overlap region 34. In thisoverlap region 34, the listener would receive information from thehigher priority one of Zone Z1 and Zone Z2. In the preferred embodiment,as will be described hereinbelow, Zone Z2 is higher priority than ZoneZ1 and Zone Z3. Therefore, the listener would have to traverse outsideof the overlap region 34 and into the exclusive portion of Zone Z1 inorder to receive commands and information from transmitter 10.

Referring now to FIG. 2, there is illustrated a diagrammatic view of thezone operation. This diagrammatic view is taken from the perspective ofa cross section through all of the zones and the method by which theyadjoin each other. As will be described hereinbelow, there are two modesthat the transmitters can operate in, these defined by a sync frequency.The receivers in the headsets worn by the listeners are able to decern achange in command frequency from a low frequency to a high frequency.The high frequency is given the highest priority. In the exampleillustrated in FIG. 2, Mode A is the highest frequency and Mode B is thelowest frequency. When the user goes from the low frequency to the highfrequency, the receiver will automatically receive commands from thehigher frequency transmitter or from Mode A. When the user traversesfrom Zone Z2 to Zone Z1, there will be a portion of the time that thelistener will be in the overlap area 34. During this time, however, thetransmitter 12 in Zone Z2 will have priority. It is only when thelistener passes outside of the overlap area 34 into Zone Z1, that thetransmitter 10 in Zone Z1 will take over and the listener will thenreceive command information therefrom. The audio information istransmitted on separate channels, such that adjacent zones do not havecommon channels. As will be further discussed hereinbelow, thesynchronizing information will be received in the form of pulses. Thesepulses have a pulse width. By incrementally varying the pulse width,commands can be sent. Again, this will be described in more detailhereinbelow. These commands allow the system to configure the operationof the receiver, as will be described in more detail hereinbelow.

Referring now to FIG. 3, there is illustrated a block diagram of thereceiver in the headset and the transmitters. The transmitter isgenerally comprised of a data block 40 for generating synchronizing andcommand information and an audio generator 42 for generating audio onmultiple channels, four channels in the preferred embodiment. Thisinformation is all sent to the modulator 44 for modulating theinformation in the form of audio and data onto separate carrierfrequencies, there being two carrier frequencies associated with eachstereo audio channel and the command/synch information. This is thenutilized to modulate an optical diode 46. As will also be discussedhereinbelow, the audio channels are binaural, such that each channelrequires two signals. Therefore, there are in effect eight audiochannels.

The receiver is comprised of an audio processing section 50 forreceiving from an optical receiver 52 the audio information on all ofthe transmitted channels. The audio processing section 50 is controlledby a data processing section 54 to only select the appropriate channeland, since it is binaural, it will actually receive both portions of agiven channel, i.e., two audio channels. These are then utilized todrive two loudspeakers 56 and 58. The data processing section 54 is alsooperable to receive the synchronization and command information from themodulated carrier that is received and decoded from the command carrierby the optical receiver 52 for processing thereof.

In one mode, a video mode, Liquid Crystal Display (LCD) shutters areoperated in a three-dimensional programming mode, this referred to byblock 60, labeled "LENS". The headset generally is described in U.S.Pat. No. 5,272,757, U.S. Pat. No. D358,151 and U.S. Pat. No. D358,158,each of which is incorporated herein by reference. These headsets areoperable to integrate a three-dimensional sound system with athree-dimensional LCD LENS system.

Referring now to FIG. 4, there is illustrated a timing diagram depictinga Mode A and a Mode B. Mode A is illustrated as a stream of pulses,which is a frequency of 24 Hz in the present invention. Mode B isillustrated as being a stream of pulses at frequency of 12 Hz. It can beseen that the pulses have the rising edge thereof synchronized. Each ofthe pulses in Mode A and Mode B can have the pulse width thereof varied.Of course, the pulse width remains constant for a predetermined numberof pulses, such that this information can be transmitted. Theinformation contained in this pulse width is the command information. Aswill be described hereinbelow, this determines whether a particularchannel is selected, whether a mute operation is selected, etc.

It can be seen from the timing diagram of FIG. 4 that, if a receiver isreceiving command information from a Mode B transmitter, and then beginsreceiving from a Mode A transmitter, it can detect the switch, since itdetects the additional pulse. However, if a receiver were receiving froma Mode A transmitter and then receives at the same time commandinformation from a Mode B transmitter, it would not recognize theadditional pulse.

When traversing from a Mode B to a Mode A transmitter, the additionalpulse would be recognized. However, if the pulse width of the Mode Btransmitter were larger than the pulse width of the Mode A transmitter,this would result in half of the pulses having a different pulse width.The software utilized to determine the pulse width is essentially asoftware counter. This counter is reset at the rising edge of the pulseand its value read at the falling edge of the pulse. A register orbuffer is provided for storing this information for each pulse. Thissystem will not declare a valid received signal until it receivesapproximately ten or more sequential pulses having the same pulse width.At that time, it will declare that it has received a pulse width of thatlength. Alternatively, however, this system could recognize that it hasreceived a higher frequency signal and discriminate the new pulse width,if the new pulse width is shorter. Of course, for a longer pulse widthin the Mode A transmitter, the falling edge of the pulse aligned withthe Mode B transmitter will be additive and it will effectively have thesame pulse width as the added pulses. It is only for the shorter pulsewidth in the Mode A transmitter that there can be a problem. The systemcan merely wait for the listener to move out of the overlap region ormake a decision based upon half of the pulses, i.e., if half have ashorter pulse width, this means that the shorter pulse width must be dueto the higher priority transmitter. If more than ten of the shorterpulses are received, this could be used to make the decision that thelistener is now in the higher priority zone. In any event, it can beseen that this is a seamless operation and merely requires a singlecommand channel wherein the command information is received from bothsystems, the Mode A transmitter and the Mode B transmitter, at the sametime, but the Mode A transmitter takes priority. By determining that achange has been made from a Mode B transmitter to a Mode A transmitter,a shorter pulse width on the Mode A transmitter will be selected as theprevailing command; that is, the system can arbitrate the reception oftwo pulse widths and select the shorter pulse width, which by designmust be due to the Mode A transmitter. It is noted that the commandchannel can have a much greater range than the program channels, suchthat the receiver can have the channel selected prior to the receiverentering the program receive zone of the transmitter by receiving thecommand from the command channel well prior to receiving the programchannels.

Referring now to FIG. 5, there is illustrated an overall block diagramof the receiver. A photo diode block 70 is provided, which containsconventionally available photo diodes, which are mounted on the headset.These are relatively broad band and operated over a frequency range of360 kHz to 3,000 kHz. This provides an output on a node 72. The node 72is input to a filter preamp circuit 74 and also to a syncpreamp/detector circuit 76. The filter/preamp circuit 74 operates over afrequency range of 360 kHz to 3,000 kHz, whereas the syncpreamp/detector circuit 76 operates at a frequency of 2.4 MHZ and/or 76kHz. This is relatively narrow operating range.

The filter preamp circuit 74 provides two channels, one on a line 78 andone on a line 80. The channel on line 78 is input to a wide band FMreceiver 82, which is then fed to an audio amplifier 84 and then to anaudio transducer 86, which audio transducer 86 is essentially one of thespeakers 56 and 58. Similarly, node 80 is fed to a wide band FM receiver88, the output of which is passed through an audio amplifier 90 to drivean audio transducer 94. The audio transducers are of the typemanufactured by Tand Corporation, Model No. 331021. The wide band FMreceivers 82 and 88 are of the type NE605, manufactured by Philips.These are relatively straight forward and conventionally availabledevices.

Each of the FM receivers 88 is controlled by various crystals 96. Thecrystals 96 are selectable to determine the frequency range or thechannel to which the FM receivers 82 and 88 are tuned. As describedabove, there are four major channels for audio reception, each channelhaving two sub-channels. Therefore, there are a total of eight channelsof audio information (although any number of channels could beaccommodated). The FM receivers 82 and 88 are tuned to two separatechannels to receive the information for the two different audiotransducers 86 and 94. Also as described above, this information is forbinaural reception.

The sync preamp/detector 76 is operable to detect and amplify the syncsignal, described above with reference to FIG. 4, and this then input toa microprocessor or micro-controller unit (MC) 98. This is aconventionally available microcontroller of the type MC68HC705J2,manufactured by Motorola, utilized in one embodiment. This generallyprovides control signals on a line 100 to drive the crystal selectioncircuit 96 and also provide signals to a lens driving circuit 101 todrive an LCD lens 102. Various built-in test operations are provided byreceiving the signal strength indicator outputs of the signal strengthindicator outputs of the receivers 82 and 88 and compare them in acomparator 104 with a reference voltage and then output the signal tothe MC 98. Various power supply operations are provided by a power-upcircuit 110 which provides power to an audio power supply 112 and asynchronizing amp power supply 114. These are utilized for powerconservation aspects of the receiver.

Referring now to FIG. 6, there is illustrated a schematic diagram of thesync preamp/detector 76. The input from the photo diode 70 is receivedon a photo diode input, configured of a negative terminal 120 and apositive terminal 122, negative terminal 120 connected to ground. Thepositive terminal is connected to one side of a capacitor 124, the otherside thereof connected to the positive input of an integrated circuit126. Integrated circuit 126 is a conventional amplifier which ismanufactured by NEC, Model No. UPC2800A. The negative input 120 is alsoconnected to one side of a capacitor 128, the other side thereofconnected to one side of a resistor 130, the other side of resistor 130connected to a negative input of the IC 126. The CO port of IC 126 isconnected to one side of a capacitor 132, the other side thereofconnected to ground. The input V_(CC1) is connected to the power supplyVIRED, the photo diode voltage. The input V_(CC2) is connected to a node134, node 134 connected to a resistor 136 to the FO input. Node 134 isalso connected to one side of a capacitor 138, the other side thereofconnected to ground. The sync output is provided on a node 212 labeled"A". The circuitry of FIG. 6 effectively provides a relatively sensitiveinput stage with a pulse output.

Referring now to FIG. 7a through FIG. 7f, there are illustrated detailedschematic diagrams of the sync pulse receiver. With specific referenceto FIG. 7a, there is illustrated one embodiment of the MCU 98 utilizinga microcontroller 220, of the type MC68HC705J2, manufactured by Motorolaand referred to with the reference "MCU". A crystal 222 is disposedacross the oscillator input to the MCU 220 with a reset signal receivedon a line 224. A capacitor 226 is disposed between the reset input andground with a resistor 228 disposed between the reset input and thepower supply V_(up). Four of the outputs, represented by lines 230, areprovided to drive four LEDs, LED1, LED2, LED3 and LED4. However, thepreferred embodiment requires less than four LEDs, as will be describedhereinbelow, and it should be understood that any number of LEDs couldbe utilized for the purpose of providing some type of display for theuser. Further, any type of display device could be utilized, including asound output.

The interrupt input "IRQ" is connected to the drain of an N-channeltransistor 234, the source thereof connected to ground and the gatethereof connected to the output of the sync amplifier/detector of FIG. 6on line 212. The IRQ input is also connected to the power supply througha pull-up resistor 236. Four lines are provided as outputs and representthe control signal line 100 that is connected to the frequencygeneration unit 96 of FIG. 5. These provide the selection of fourseparate frequencies or, as will be described hereinbelow, four separatecrystal pairs. Three separate lines 238 are provided that are operableto drive the LCD lens 102, these input to the lens driver 101. Anotheroutput on a line 240 is provided for driving an inverter 242 to providean output V_(AUD) which is output to the audio receiver, this being acontrol signal. A low signal on the output thereof causes the voltageV_(AUD) to go high.

A switch input on a node 225 is received from the audio board which isconnected through an RC network comprised of a resistor 227 and acapacitor 229 to an input of the MCU 220. A pull-up resistor 231 isconnected between node 225 and the power supply signal V_(up). Thisprovides a switch input from the audio board, as will be describedhereinbelow.

Referring now to FIG. 7b, there is illustrated a schematic diagram ofthe driving circuit for driving the frequency generation unit 96. Thedriving unit is comprised of four bipolar NPN transistors 244, 246, 248and 250 having the collectors thereof connected to the positive supplyand the emitters thereof for providing driving signals XTAL1, XTAL2,XTAL3 and XTAL4 to the frequency generation unit 96, these beingbasically emitter follower transistors, as will be describedhereinbelow.

Referring now to FIG. 7c, there is illustrated a schematic diagram ofthe lens driver 101. Each of the three lines 238 provide the drive forthe left lens, the common terminal for the lens and the right lens,respectively. The left lens one of the lines 238 is input through adriver 252 to drive the gates of a complimentary coupled P-channeltransistor 254 and N-channel transistor 256, the output thereof drivingan output line 258 from a stepped up voltage V_(LCD) through a resistor260. Similarly, the one of the lines 238 associated with the commonterminal of the lens is passed through a driver 260 to the gates of twocomplimentary coupled transistors, a P-channel transistor 262 and anN-channel transistor 264 to drive an output 268 from the stepped upvoltage V_(LCD) through a resistor 270. The one of the lines 238associated with the right lens is passed through a driver 272 to thegates of two complimentary coupled transistors, a P-channel transistor274 and an N-channel transistor 276 to drive an output terminal 278 fromthe stepped up voltage V_(LCD) through a resistor 280. This provides theright lens driver. V_(AUD) provides audio power control to turn off theaudio portion of the board under the control of the MCU 220. A separatedriver 282 is provided for having the input thereof connected to the oneof the lines 238 associated with the right lens and providing a senseoutput on a line 284 which is not utilized.

Referring now to FIG. 7d, there is illustrated a schematic diagram ofthe lens voltage set-up for generating the voltage V_(LCD). A step-upswitching regulator 290, of the type MAX630 manufactured by Maxim, isconfigured in a conventional manner with a switching inductor 292connected across the inductor terminals with one side thereof connectedto a node 294 and the other side thereof connected to a VDD terminal296. A Schottky diode 300 has the anode thereof connected to node 294and the cathode thereof connected to a node 302, this comprising theV_(LCD) voltage. A capacitor 304 is connected between node 302 andground. The node 302 is also connected through a resistor 306 to the VFBinput of the switching regulator 290 with a capacitor 308 disposed inparallel with the resistor 306. A resistor 310 is connected between theVFB input and ground V_(DD) is the power supply input. The nid-point ofa resistive divider comprised of a resistor 312 and resistor 314connected between the positive voltage supply VAMP and ground is inputto a comparator input to the circuit 290.

Referring now to FIG. 7e, there is illustrated a schematic diagram of amicro-power supervisor which is operable to receive the power-on syncvoltage VDD, which is used as the input for the step-up voltageregulator of FIG. 7d. The supervisor of FIG. 7e utilizes an integratedcircuit of the type MAX666, manufactured by Maxim, which is amicropower, low voltage regulator which regulates the power signalV_(DD) down to V_(UP), the power for the microcontroller 220. Theintegrated circuit 320 is operable to have the sense input connected tothe signal V_(UP) that is operable to power the MCU 220 and also havethe VSET input connected to a sense node 322, which is connected to thejunction between two series connected resistors 324 and 326, withresistors 324 and 326 connected between the power supply voltage V_(UP)and ground. The input voltage is connected to node 296 with the voltageVDD disposed thereon with the reset signal on line 224 input on aterminal LBO and a scaled down voltage signal input to an input LBI, thescaled down voltage input signal received from the mid-point of twoseries connected resistors 328 and 330 that are configured as a voltagedivider connected between the voltage VDD and ground. The LBI signal isa scaled down V_(DD) input to an internal comparator for comparison toan internal reference to generate the reset signal and reset themicrocontroller 220 if V_(DD) falls below a threshold level.

Referring now to FIG. 7f, there is illustrated a schematic diagram ofthe power on sync circuit. The power on sync circuit is operable toreceive the output voltage from the sync preamp/detector 76 on line 212,this signal input through a resistor 332 to the gate of an N-channeltransistor 334. A capacitor 336 is connected between the gate oftransistor 334 and ground. The source of transistor 334 is connected toground and the drain thereof connected to a node 338. Node 338 is alsoconnected to the voltage VAUDB on a node 340 through a parallelconnected resistor 342 and capacitor 344. Node 338 is also connected tothe gate of a P-channel transistor 346, the source to the node 340 andthe drain connected to voltage terminal 296 that supplies the VDDvoltage. A capacitor 348 is connected between node 296 and ground and acapacitor 350 is connected between node 340 and ground. The batteryvoltage V_(batt) is input on a terminal 352, which comprises the audiovoltage VAUD. This is connected through a Schottky diode 354 to the node340 to provide the VAUDB voltage. Similarly, the voltage VAMP on a node356 is provided by connecting node 352 to the anode of a diode 358, thecathode thereof connected to node 356. Therefore, whenever the syncsignal is detected by the detector 76, line 212 will go high, turning ontransistor 334 and pulling node 338 low. When node 338 goes low,transistor 346 will pull node 296 high, thus providing the voltage VDD.

Referring now to FIG. 7g, there is illustrated a timing diagram for thelens driver illustrating a sync signal waveform, a common waveform andthe L/R control. It can be seen that the sync signal on a falling edge360 is synchronized with a rising edge 362 of the common signal. After arising edge 364 on the sync signal, a rising edge 366 on the L/R signalwill occur. However, it is not necessary that the rising edge of thesync signal specify the pulse width of the lens driving signals, and itneed not precede the rising edge of the L/R signal. The left lens signalis illustrated which varies between 15 volts, 0 volts and -15 volts.When the lens is on, it is at 0 volts. Thereafter, it must alternate inthe off state between -15 volts and +15 volts. Therefore, whenever thecommon signal goes high at edge 362, a common voltage or ground isconnected to the L/R input and +15 volts is connected to the commoninput of the lens, this resulting in a reverse polarity level 368. Atedge 366, both the common and the L/R input are connected to +15 voltsto result in 0 potential thereacross. At falling edge 370 on the commonsignal, the common signal is pulled back to ground, thus resulting in areverse polarity signal at a level +15 volts on the lens drive signal,represented by a point 372 on the left lens waveform. As such, it can beseen that the lens is cycled off at the falling edge of the sync signaland then turned back on at the rising edge of the L/R signal and thenturned off again at the next falling edge of the sync signal. However,for alternating falling edges at the sync signal, the polarity acrossthe lens is reversed. This is a conventional operation for driving LCDs.

Referring now to FIG. 8, there is illustrated a schematic diagram of theaudio receiver. The schematic of FIG. 8 refers only to one channel, theright channel. However, it should be understood that the left channel isidentical, with the exception that different frequencies are selected.The signal on node 72 is input to the gate of an N-channel transistor380 which has the source/drain path thereof connected between a node 382and a node 384. A plurality of tank circuits 386 are connected in seriesbetween the node 382 and the voltage VREG. Voltage VREG is a voltagethat is derived from the VDD voltage through a regulation circuit toprovide a regulated voltage therefrom. In the preferred embodiment,there are four tank circuits, each comprised of a parallel connectedinductor capacitor. This provides a bandpass filtering function. Thenode 384 is connected through a resistor 390 to ground, resistor 390being paralleled with a capacitor 392. There is a similar preamp circuitdisposed on the left channel for providing the appropriate filtering.

The right channel operates for four frequencies, there being a total ofeight frequencies, such that four frequencies are associated with theright channel and four frequencies are associated with the left channel.This allows eight separate audio channels and, since they are binaural,this allows for four separate binaural channels. Of course, the numberof channels is merely limited by the number of frequencies that can beutilized in the passband of the audio receiver.

Node 382 is connected to an input of a super heterodyne integratedcircuit 394, which is of the type NE605, manufactured by Philips. Thisis a conventional circuit. The receiver 394 utilizes a 10.7 MHZ IFfilter 398 which is connected between an IF signal on a line 400 that isoutput from an internal mixer, and an output provided on a line 401 asan input to an IF amplifier (not shown). The output of the internal IFamplifier is provided on a line 402, this then input to a 10.7 MHZ IFfilter 404. This is input to an internal limiter (not shown) on lines406, the output thereof input to an internal mixer (not shown) whichalso receives an input from a discriminator 410. This then provides theoutput signal on a line 412. Additionally, there is an internal functionthat is associated with this circuit that provides a measure of receivedsignal strength, this being a Receive Signal Strength Indicator Signal(RSSI) on a node 414. This is utilized for testing purposes and squelchpurposes.

An internal oscillator is provided across two nodes 416 and 418. Node418 is connected through a capacitor 420 to ground, with a capacitor 422connected across nodes 416 and 418. Node 416 is operable to be connectedto one side of a crystal, the other side thereof operable to beconnected to ground. In the present embodiment, four switchable crystals424, 426, 428 and 430 are provided, each having one side thereofconnected to the terminal 416. The other sides thereof are connectedthrough resistors 432, 434, 436 and 440, respectively, to the selectsignals SEL4, SEL3, SEL2 and SEL1, respectively. Each of the other sidesof the crystals 424-430 are connected through associated diodes 442,444, 446 and 448, respectively, to ground. Therefore, when either of thesignals SEL1-SEL4 is pulled high through the transistors 244-250 of FIG.7b, this will cause current to flow through the selected one of thediodes 442-448 to bias the other side of the selected crystal 424-430.In this manner, the frequency range can be selected on the receiver 394.

The node 412 is connected through an audio amplifier 450 to provide thespeaker drive signal, the amplifier 450 having a mute input. This is alow power audio amplifier of the type MC34119, manufactured by Motorola.

Referring now to FIGS. 9a and 9b, there is illustrated a schematic blockdiagram of a portion of the audio/sync receiver that provides thepreferred embodiment of the MCU 98 and some of the control functions tointerface with the user. A comparator 460 receives on the positive inputthereof a voltage that is derived from a resistive divider comprised oftwo resistors 462 and 464 connected between the battery voltage VBAT andground. The negative input of comparator 460 is connected to a node 462,which is connected to one side of a zener diode 466, this providing areference voltage. This comparator 460 is powered by the voltage VDD.The comparator 460 determines whether the voltage of the battery hasfallen below a predetermined value, as defined by the value of theresistors 462 and 464. This drives an output node 468 that is connectedto an input of a micro-controller unit (MCU) 470 of the type PIC16C61,manufactured by Microchip Technology, Inc. Additionally, there areprovided two LEDs, a red LED 472 which is oriented such that the anodethereof is connected to node 468 and the cathode thereof is connected toa node 474, and a green LED 476, oriented in the opposite direction ofLED 472 and connected in parallel therewith. Node 474 is connectedthrough a resistor 478 to a second input of the micro-controller 470through a resistor 491. Therefore, whenever node 468 is high and theother side of 478 is low, the green LED 476 will be on. The red LED 472will be on under the opposite conditions.

A second comparator 480 is provided having the negative input thereofconnected to the reference voltage of node 462 and the positive inputthereof connected to the RSSI output from the audio receivers. Thiscorresponds to the comparator 104 of FIG. 5. This provides an outputthat is connected to a separate input on the micro-controller 470. AnAudio Off signal is an output on a line 484 from the microcontroller 470to power down the audio section. The sync signal is received on a line486 with the four crystal select signals XTAL1'-XTAL4' generated onlines 400. A push button switch 490 is provided for the user tomomentarily connect a ground voltage through a resistor 491 to the inputthat is connected to the other side of the resistor 491. Therefore,whenever this is grounded and node 468 is high, the green LED 476 willturn on. This, of course, will be the normal operation, since the outputof comparator 460 will be high when the battery voltage is good. As willbe described hereinbelow, the user depresses the button 490 to inputground to the micro-controller 470, such that a channel can be selectedwhen a User Channel mode is entered. This is a situation that occursduring the language selection in a theater environment. When the switch490 is depressed, this will pull the cathode of the green LED low and itwill be illuminated. Additionally, there is provided a switch 492 thatis connected between ground and an input node 496 through a resistor494. A pull-up resistor 498 is connected from node 496 to the voltageVDD. This is a theater/museum switch, such that, in one position, awalking tour arrangement will be selected for and, in the otherposition, a theater environment will be selected. The switch alsochanges the timeout on data invalid. The node 496 is labeled LCS_(LR),which is the left-right control signal for the lenses. This is passedthrough an inverter to provide the right signal, with this node 496providing the left signal. A common signal is provided on a node 500,these then comprising the lines 238 described above with reference toFIG. 7 and these input to the lens driver 101.

The overall operation of the system will be described with respect toTable 1, which Table 1 sets forth the various modes. There are variouspower defining states to define whether the MCU is powered, the syncreceiver is powered, the IR string is powered, the audio system poweredor the shutters are powered. The shutters are the LCD lenses, which aretypically utilized only in the theater scenario, but can be utilized ina situation wherein a walking tour requires both the use of the shuttersand the audio portion. This is referred to as a full operation headsetsystem. Table 1 is as follows:

                                      TABLE I                                     __________________________________________________________________________    POWER                                                                              OPER  STATE               SECTIONS                                       STATE                                                                              STATE CONDITIONS          POWERED   Comments                             __________________________________________________________________________    1    Asleep                                                                              Battery installed - no user action sync <                                                         MCU       Sleep after 5                                   8 Hz                          seconds.                             2    Wake up                                                                             Battery installed - button pushed, no IR                                                          MCU       Timeout after 2                           sense sync modulation     sync receiver                                                                           seconds. IR and                                                     IR string Audio power                                                                   down.                                2    Wake up                                                                             Sync > 8 Hz detected                                                                              MCU                                                 detected                  sync receiver                                                                 IR string                                      3    Self test                                                                           37 Hz < Sync < 43 Hz                                                                              MCU       MCU allows                                      Pulse width = 1 ms: mute-audio pwr off.                                                           sync receiver                                                                           channel changes                                 Pulse width = 2 ms: user channel                                                                  IR string                                                 Pulse width = 3 ms: channel #1                                                                    audio                                                     Pulse width = 4 ms: channel #2                                                                    shutters (turning on                                      Pulse width = 5 ms: channel #3                                                                    and off slowly)                                           Pulse width = 6 ms: channel #4                                                Pulse width = 7 ms: user channel                                              Pulse width = 8 ms: mute-audio                                                pwr off.                                                           4    Audio only                                                                          8 Hz < Sync < 14 Hz or                                                                            MCU       MCU allows only                                 15 Hz < Sync < 19 Hz                                                                              sync receiver                                                                           one channel                                     20 Hz < Sync < 28 Hz                                                                              IR string change                                          Pulse width = 1 ms: mute-audio                                                                    audio (unless Pulse                                       pwr off.            width = 1 ms or 8 ms)                                     Pulse width = 2 ms: user channel                                              Pulse width = 3 ms: channel #1                                                Pulse width = 4 ms: channel #2                                                Pulse width = 5 ms: channel #3                                                Pulse width = 6 ms: channel #4                                                Pulse width = 7 ms: user channel                                              Pulse width = 8 ms: mute-audio                                                pwr off.                                                           5    Shutters only                                                                       43 Hz < Sync < 100 Hz                                                                             MCU                                                       Pulse width = 1 ms or 8 ms                                                                        sync receiver                                                                 IR string                                                                     shutters                                       3    Full  43 Hz < Sync < 100 Hz                                                                             MCU       MCU allows only                           operation                                                                           Pulse width 1 ms: mute-audio                                                                      sync receiver                                                                           one channel                                     pwr off.            IR string change                                          Pulse width = 2 ms: user channel                                                                  shutters (flashing at                                     Pulse width = 3 ms: channel #1                                                                    sync rate)                                                Pulse width = 4 ms: channel #2                                                                    audio (unless Pulse                                       Pulse width = 5 ms: channel #3                                                                    width = 1 ms or 8 ms)                                     Pulse width = 6 ms: channel #4                                                Pulse width = 6 ms: user channel                                              Pulse width = 8 ms: mute-audio                                                pwr off.                                                           8    Set Max                                                                             29 Hz < Sync < 37 Hz                                                                              MCU       Allow channel                             Channel                   sync receiver                                                                           change and set max                                                  IR string channel to FORCE                                                    shutters  CHANNEL value                        __________________________________________________________________________

Referring now to FIGS. 10a and 10b, there is illustrated a flowchartdepicting the overall operation as noted in Table 1. The flowchart isinitiated at a start block 512 and then proceeds to a function block 516to power the MCU and then to a decision block 514 to determine if thebattery level is acceptable. If not, the program will return to theinput of decision block 514. When a battery voltage is acceptable, theflowchart will flow to a decision block 518 to determine if there is anyuser action. If not, the program will flow along an "N" path to a sleepfunction block 520 and then to the decision block 514 and the programwill not be executed. This is determined by comparing battery voltage toan operational threshold and, if it exceeds this threshold, the batteryis declared present. When user action is detected, the flowchart flowsto a decision block 522 which determines if a sync signal has beenreceived. If the sync signal has not been received, then the flowchartflows to a decision block 524 to determine if the button has been pushedby the user. If not, the program will flow along an "N" path back todecision block 514. If a button has been pushed, the program flows alonga "Y" path to power the sync receiver and then process the buttoncommands to store the selected channel by the user. The flowchart willthen flow back to decision block 514.

When the sync signal is detected, the flowchart will flow from decisionblock 522 to a decision block 528 to determine if the sync rate isgreater than 8 Hz. If not, the program will flow back to the input ofdecision block 514 through the sleep block 520. When the sync rate isabove 8 Hz, the flowchart will flow to a decision block 530 to determineif the sync rate is between 37 and 43 Hz, wherein it will then flow to aself-test block 532. If it is not in this range, the flowchart flows toa decision block 534 to determine if it is between 8 and 14 Hz, 15 and19 Hz, or 20 and 28 Hz. If so, the flowchart flows to a function block536 to define it as an audio only mode. If it is not in that range, theflowchart flows to a decision block 538 to determine if the range isbetween 43 and 100 Hz. If so, the flowchart will flow to a decisionblock 540 to determine if the pulse width is 1 ms or 8 ms. If so, thiswill define a shutter only mode and turn power off using line 484 ofFIG. 9. If not, the flowchart will flow to a decision block 544 todetermine if the pulse width is set to 2, 3, 4, 5, 6 or 7 ms. If so,this indicates a full operation function block 546. If it is not 2 and 7ms inclusive, the flowchart will flow along an "N" path and return tothe decision block 520. If decision block 538 determines that the rangewas not 43-100 Hz, the output of decision block 538 would flow to adecision block 550 to determine if the sync rate was between 29 and 37Hz. If so, the program would flow to a function block 552 to set themaximum channel. If it was determined that none of the sync rate rangeswere present, the program would flow back to the input of decision block514 through sleep block 520.

Referring now to FIGS. 11a and 11b, there is illustrated a flowchartdepicting the operation of the Audio Only mode. The flowchart isinitiated at a block 570 and then proceeds to a function block 572wherein N is set equal to 0. The program then flows to a decision block574 to determine if a pulse has been received. If not, the program willflow back to the input of decision block 574. When a pulse is received,the program flows to a function block 576 to increment the value of Nand then to a decision block 578 to determine if the value of N is equalto 10. If not, the program will flow back along the "N" path to thedecision block 574. This will continue until ten pulses have beenreceived. At this time, the program will flow along a "Y" path to afunction block 580. The loop back operation with respect to decisionblock 578 and decision block 574 is to require at least ten valid pulsesto be received, a valid pulse defined as a pulse having the same pulsewidth. If a pulse of another width is received, this will cause thesystem to reset--the counter N resets and the new pulse width isrecognized after N=10.

The function block 580 determines what the pulse width is of the pulsesbeing received. This is measured and then the program flows to adecision block 582 wherein it is determined whether the pulse width is 1ms. If so, the program flows to a function block 584 wherein the systementers a mute operation and the audio power is turned off. If the pulsewidth is not 1 ms, the program will flow to a decision block 586 todetermine if the pulse width is 2 ms. If so, the program will flow to afunction block 588 to utilize or select the user defined channel. Asdescribed hereinabove, each user has the ability to push a button toselect one of the four channels on which to receive audio information.Once this selection is made and stored, it is then only necessary toenter this mode via receiving a command in the form of a 2 ms pulsewidth in the Audio Only mode or Full Operation mode.

If the 2 ms pulse width was not received, the program flows to adecision block 590 to determine if the pulse width is 3 ms. If so, theprogram flows to a function block 592 wherein channel 1 is selected.Subsequent decision blocks 594 associated with a 4 ms determination, 596associated with a 5 ms determination and a decision block 598 associatedwith a 6 ms determination will route the program to respective functionblocks 600, 602 and 604 where selection of channels 2, 3 and 4,respectively, will be actuated.

If none of channels 1-4 have been selected, the program will flow fromdecision block 598 to a decision 606 to determine if the pulse width is7 ms. If so, the program will flow to a function block 608 to select theuser defined channel. If the pulse width is not 7 ms, the program willflow to a function block 610 to determine if the pulse width is 8 ms. Ifso, the program will flow to a function block 612 to enter the muteoperation and turn the audio power off. If it is not 8 ms, the programwill flow to a decision block 613 to determine if there has been achange in the sync frequency. If not, the program will flow to a returnblock to the main program and, if so, the program will flow to afunction block 614 to unlock a channel, which will be describedhereinbelow. The program will then flow back to the input of the returnblock.

Each of the function blocks 584, 588, 592, 600, 602, 604, 608 and 612each flow to a decision block 618 to determine if the channel is locked.The channel is locked whenever a sync change has occurred and a pulsewidth is determined and a channel selected or a mode of operationselected. Once a mode of operation is selected, it is then necessary fora synchronization frequency change to occur in order to allow anotherchannel to be selected. Once selected, the channel is locked and pulsewidth changes thereafter will not change it. Therefore, if the channelis locked, the program will flow along a "Y" path from decision block618 to the input of decision block 613 to determine if a synchronizationchange has occurred. If not, the program will continue to follow thispath. However, once a synchronization change has occurred, the programwill flow to decision block 618, after a channel has been selected, andthen set or select that channel and then lock it. This is indicated by afunction block 620. The program will then flow back to the input ofdecision block 613 and continue along this path. This won't occur untila synchronization change has occurred and the channel is unlocked atfunction block 614 and then the program will flow to function block 620to set the new channel.

Referring now to FIG. 12, there is illustrated a diagrammatic view ofthree zones, Zone 1, Zone 2 and Zone 3, Zone 1 separate from Zone 3 but,Zone 1 and Zone 3 adjacent to Zone 2. There is illustrated a generalsystem synchronization device 630 which is operable to generate the syncsignal which is delivered to three transmitters 632, 634 and 636.Transmitter 632 has a synchronization rate of 12 Hz, transmitter 634 hassynchronization rate of 24 Hz and transmitter 636 has synchronizationrate of 12 Hz. In Zone 1, the transmitter is operable to transmit overthree channels, channels 2-4, this operating in an Audio Only mode.However, the transmitter 632 is limited to only transmitting on channel2, channel 3 and channel 4. The transmitter 634 is limited totransmitting only on channel 1, whereas transmitter 636 is operable totransmit on channels 2-4. Each of the transmitters 632-636 hasassociated therewith an emitter array 638, 640 and 642, respectively.

It can be seen that in Zone 1, there are multiple listeners listening toaudio channels 2, 3 and 4. When a listener moves from Zone 1 to Zone 2,that listener experiences a sync change and, upon noticing it, will thenlook for a valid pulse width. Zone 2 transmits only on channel 1 and,therefore, will only transmit pulse widths of 3 ms. As soon as all ofthe pulses have a pulse width of 3 ms, the system will recognize thisand will then perform the channel selection. However, alternately, thesystem can recognize that it previously had received pulse widthsgreater than 3 ms and recognize that a pulse has been inserted at thehigher frequency. The system can contain the sophistication to allow itto select this pulse width, if necessary. However, it is only necessaryto allow the user to move far enough out of the range of Zone 1 to allowit to receive only on channel 1. Typically, channel 1 is backgroundmusic that is played between exhibits. Further, the transmitter 634 andZone 2 could be set to a mute channel with a pulse width of 1 ms or 8ms.

When the user traverses between Zone 2 and Zone 3, it will recognizeanother sync change from 24 Hz to 12 Hz. Of course, this will occur onlyafter the transmitter power from transmitter 634 is lost, such that theextra pulse is removed at the reduced sync frequency. When this occurs,the pulse width associated with the transmit command for channels 2, 3or 4 will be received. However, it is important to note that only onecommand can be transmitted.

The typical scenario for a walking tour is that one set of individualsor group of individuals will come in to a zone at different times. Eachzone will have a predefined program of a predetermined length to beplayed over the audio channel. It is desirous that, when the individualenters the zone, the program be initiated upon that event occurring. Inorder to facilitate this, the system must first sense that the person orgroup has entered the transmitting area and then initiate the program ona given channel. However, the problem occurs when the second individualor group of individuals enters the zone and desires to initiate theprogram. First, their headsets will receive the channel command that isbeing transmitted. If the channel command is the channel associated withthe already initiated program, then that individual or group ofindividuals could receive the program in the middle of the program, thisnot a desirous situation. The present system utilizes a staggeredstart/stop method to ensure that as many individuals as possible can beaccommodated upon entering the zone at different times. For example, ifa first individual enters the zone, his presence is sensed by either aninfrared or motion detector or by merely pressing a button on thedisplay to initiate the program. When the program is initiated, thesystem will select a channel for transmission of audio information andtransmit this command to the receivers in its transmitting area. Thereceivers will then receive this command and select the channel and then"lock" their receivers on that channel. The transmitter will theninitiate transmission of the audio program. When the next individualenters the zone, this system will again detect that presence. If apredetermined period of time has elapsed since the program wasinitiated, for example, one minute, it is desirous to start the programfrom the beginning of the program for that individual. To facilitatethis, this system first senses the presence of the individual and thensends out a command for another channel. Even though the individual withthe headset that is already listening to the program receives this newchannel select command, that receiver is locked and the previousindividual will not have the channel associated with its receiverchanged. Only the new listeners will have their receivers locked to adifferent channel. Once set to that channel, they again are locked andwill receive the new program on the new channel that is initiated at thebeginning of the program. This will continue until all of the channelsare utilized. Once all the channels are utilized, the system willcontinue to transmit the last channel command and the associated pulsewidth until a channel is free. A delay can be implemented, such thatsubsequent individuals that enter immediately after the initiation ofthe program will be directed to the same channel until a predeterminedamount of time has elapsed. After this time, the next channel will bethe select channel and any individuals entering the zone thereafter willreceive information on the next channel, the initiation of the programassociated therewith occurring upon the sensing of the first individualentering the zone.

By way of example, if large exhibit floors were provided with manyvendor areas, each with its own program material, this would require thereceiver to handle up to four different languages. Each vendor area isseparately illuminated with spot like type emitter panels so there wouldbe a separation between the zones. Each vendor area would then have itsown four-channel transmitter, a channel provided for each language.Users then would enter the exhibit floor through a staging area wherethey receive their headset and then manually select the language theywish to hear with the button. The headset automatically stores thisinformation. As the users leave the staging area, they also leave any IRfield, which causes the receiver to automatically go into mute state andthen sleep mode if the duration is long enough. Upon arriving on theexhibit floor, users are free to visit any vendor exhibit in any order.As they enter the vendor area, their receivers automatically unsquelchand switch to the stored language channel (set in the staging area) andthe user joins the narration program already in progress in the languageof their choice. In this mode, they cannot have individualizedstart/stop times, since there are four different languages in thepresent embodiment utilizing four channels. However, if sufficientchannels were provided for each language, then this could befacilitated.

In this example, each vendor exhibit would have a four-channeltransmitter continually sending four languages on the four channels. Thecommon area is sending 12 Hz sync pulses with a mute pulse width. As theuser enters the vendor exhibit zone IR field, the receiver would receivethe command to use the previously selected channel, the user channel.Since program material is available, the unit then un-mutes and the userhears the language of choice on the channel that was selected by theuser. If the user changes his/her mind and leaves the exhibit area tovisit another, operation is totally automatic and seamless, i.e., thereceiver simply stops receiving the current vendor area material andbegins receiving the new vendor program material in the correctlanguage, this facilitated simply by the user walking between zonedareas.

Referring now to FIG. 13, there is illustrated a flowchart for theoperation of the transmitter during the staggered start/stop operationdescribed above. The program is initiated at a start block 650 and thenproceeds to function block 652 to set the value of N equal to 1. Theprogram then flows to a function block 654 to set the internal selectedchannel to the value of N and then transmit this pulse width as acommand. The program then flows to a decision block 656 to determine ifa person or individual has been sensed. As described hereinabove, thesensing operation is either the depression of a switch by an overt actof the individual or by sensing the presence of the individual via sometype of motion sensor, electric eye, or other such device. Until aperson is sensed, the program will flow along an "N" path back to theinput of decision block 656. Once a person is sensed, the program willflow along a "Y" path to a function block 658 to transmit the audio onthe selected channel. The program will then flow to a decision block 660to determine if the value of N is maximum. If not, the program will flowto a function block 662 to increment the value of N and then flow backto the input of the function block 654 to set the command to the nexthigher pulse width and associated channel. When the next person issensed, they, of course, have already received the transmitted commandand the program will be initiated upon sensing. This will continue untilall the channels have been utilized. If the value of N is maximum, theprogram will flow along a "Y" path from decision block 660 to decisionblock 664 to determine if the program on channel 1 is finished. If not,the program will flow back to the input of function block 654 tocontinue transmitting the command of the last channel. When channel 1 isfinished its program, the program will flow along the "Y" path fromdecision block 664 to the input of function block 652 to again providechannel 1 as the selected channel.

In a theater setting, the pulse width information is utilized to conveyto the receiver information regarding use of a user selected channel. Inthis mode, the available commands would be as follows:

pulse width=1 ms: mute

pulse width=2 ms: user channel

pulse width=3 ms: channel #1 only available

pulse width=4 ms: channels #1 and #2 only available

pulse width=5 ms: channels #1, #2 and #3 only available

pulse width=6 ms: all channels available

pulse width=7 ms: user channel

pulse width=8 ms: no channels available (audio board off/shutters only)

If, for example, a theater has only two languages available (channels 1and 2), it is possible to prevent the user from selecting channel 3 orchannel 4, thus allowing all of the available emitter panel power to bedevoted to channels 1 and 2. In this case, the transmitter wouldbroadcast a 4 ms pulse width telling the receiver that two channels areavailable. A jumper inside the receiver (not shown) determines how thereceiver should respond to the pulse width information. The pulse rate(sync frequency) information would remain as described in the abovetable. Alternately, the "SET MAX CHANNEL" frequency could be utilized todetermine which channels are available.

Referring now to FIG. 14, there is illustrated a block diagram for atwo-way transmission embodiment. In FIG. 14 there is illustrated areceiver 670 and a system transmitter 672. The system transmitter 672has a system sync block 674 and an audio block 676, the shutteroperation not illustrated. The audio block 676 is controlled by acontrol block 678 which receives synchronization information from thesynchronization block 674. An emitter array 680 is provided fortransmitting information to the receiver 670, which receiver 670 has areceiver 682 associated therewith. The operation up to this point hasbeen as described hereinabove. However, in addition to the receiver 682at the receiver 670, the receiver 670 also contains a transmitter 684,which transmitter 684 transmits on a separate frequency apart from thetransmitter 680 and the receiver 682. This could be a wireless radiofrequency or it could be an optical IR channel. The only requirement isthat a transmitter 684 be provided in the receiver 670 and acorresponding receiver 686 be provided in the system transmitter 672 toprovide a separate and independent communication path.

The use of a two-way communication path would allow for two things.First, information now can be transmitted to the system transmitter forthe purpose of determining that the headset is within its transmitrange. Additionally, ID information can be transmitted to thetransmitter with additional configuration information. For example, thedesired channel on which information is to be received could betransmitted to the system transmitter from the headset, such that thesystem transmitter will then initiate the desired information to theheadset. For example, in a security mode, one individual may have aunique access to a particular channel in a zone. This information wouldnot be transmitted until the appropriate individual were in the zone.

When the user initially receives the headset, the headset is in apowered-off mode of operation. The user then merely pushes the button onthe side of the headset, which instructs the MCU to start running andwait to be commanded into some operational state by the IR link.Alternately, when the headset is powered up, if it is within a syncfield, it will see a valid sync pulse within the five second period andwill continue operating. However, after five seconds, the system willpower down and go to sleep and wait for some user operation to wake itup.

Once the button is pressed and the MCU detects a valid command, thereceiver enters the appropriate operational mode and may, depending onthe mode, begin to use the switch for audio channel selection. Thisswitch is utilized in the user mode only or the set max channel mode.When in this mode, hereinafter referred to as "user channel mode", theuser may change audio channels by pushing the button.

Although not implemented in the preferred embodiment, one method ofoperation would be as follows. The first push of the button on theheadset that is "awake" causes the LED to indicate which channel hasbeen selected, as described above, but does not change the channels. Ifthe button is pushed again within some time out period (ten seconds inthe preferred embodiment), then the channel is changed to the nexthigher channel, i.e., channel 4 changes to channel 1, and the LED blinksn times for the channel number n to reflect this change. After the timeout period, pushing the button merely causes the LED to indicate theselected channel and does not change the channel.

The button may also be utilized to enter an enhanced test mode. If thebutton is pressed and held down while the battery is installed, the redLED flashes red until it receives a valid sync signal. This is includedto make photo-diode failures more evident to the user. Without thisfeature, a failure in the sync signal chain would be indicated by anabsence of a red or green LED flash.

An internal switch (not shown) is accessible through a cover on theheadset. This switch is utilized to select the default data channelabsent time out. The standard time out is two minutes to conservebattery life. If a receiver does not see valid data for two minutes, itgoes to sleep. The user then must press the button to wake it up. In awalking tour application, the user may be out of an IR field forextended periods of time. This is especially true for exhibits that havefew panels spread out with no wide-area emitter panels to cover thegaps. Selecting the non-theater mode increases the default time out toinfinity.

Visual indications regarding the above-described modes of operation aregenerally noted by the user via the LED indicator. During the time theuser has the headset in his/her possession and no modulated synccarriers are being emitted from emitter panels, i.e., the syncmodulation is less than 8 Hz, no illumination of the LED will occur evenif the user pushes the button. When the sync modulation exceeds the 8 Hzrate and a single button push by the user occurs, the receiver then"wakes up", i.e., the MCU starts looking for commands over the IR datalink. However, it should be understood that multiple LEDs as describedabove could be utilized, or a liquid crystal display panel could beutilized to provide more information.

The red LED is utilized to indicate a fault condition. A solid red LEDindicates a battery fault. When in Test Mode, failure of self test isdetected by reading an RSSI bit from the receiver. The MCU indicates theself test failure by a flashing red LED.

Initiation of self test mode does not light either LED. Successfulcompletion of a self test is indicated by a flashing green LED. The rateof flash is determined by the rate of change of the pulse widthinformation. The LED flashes the status (red-fail, green-pass) onsuccessful determination of the pulse width associated with forcing thesystem to channel 1. The rate at which the lenses switch is alsodetermined by the rate of pulse width change. Lens change occurswhenever the pulse width is associated with a force to channel 1 (3 ms)and the user channel pulse width (2 or 7 ms) or channel 3 select (5 ms).When the transmitter is forcing the channel setting, the button isignored by the receiver, unless the Set Max Channel Mode (32 Hz) or theUser Channel Mode (Pulse Width=2 or 7 ms).

Referring now to FIG. 15, there is illustrated a block diagram of thetransmitter. Each of the transmitters have four audio channels, eachaudio channel referred to as PSE1, PSE2, PSE3 and PSE4, each having leftand right inputs 690 and 692. They are input through amplifiers 694 and696, respectively, to a filter device 698. The filter device iscomprised of a crossover device 700 for the left channel and a crossoverdevice 702 for the right channel. An equalizer circuit 704 is disposedin the left channel between the crossover circuit 700 and a pre-emphasiscircuit 706. Similarly, an equalizer 708 is disposed in the rightchannel between the crossover circuit 702 and a pre-emphasis circuit710. The outputs of pre-emphasis circuits 706 and 710 are input to alimiter 712, the limiter 712 having a left channel limiter 714 and aright channel limiter 716 disposed therein. The output of the limiters714 and 716 are input to a modulator 718 having a left channel modulator720 and a right channel modulator 722 associated therewith. The leftchannel modulator 720 is output through a potentiometer 724 to a summingcircuit 726 and the right channel limiter 722 is input through apotentiometer 728 to the summing circuit 726. Each of the signal pathsfor the limiter 720 and 722 through the potentiometer 724 and 728 arepassed through an on board connector 736 and 738, respectively. Theseswitches 736 and 738 can be removed to disable the channels.

The output of the summing junction 726 is passed through a potentiometer740 to set the level thereof to four separate output terminals 742, 744,746 and 748, respectively, through drivers 750, 752, 754 and 756,respectively. The RF output terminals are connected to the base of adriving transistor which is operable to drive an emitter diode.Typically, there are plurality of transistors having the gates thereofconnected to each of the output terminals 742-748, such that there arefour arrays.

In addition to the outputs of the modulators 718, the summing junctionis also operable to receive the output of an ASK modulator 760 and afrequency switch key (FSK) modulator 762. The ASK modulator 760 isoperable to modulate the carrier at a frequency of 76 kHz, whereas theFSK modulator is operable to modulate a carrier of 2.45 MHZ. The FSKmodulator 762 and ASK modulator 760 are controlled by a micro-controllerunit (MCU) 764. The ASK modulator 760 is further controlled by a zerocrossing detector 766. The zero crossing detector 766 ensures that theASK modulator 760 only turns on when the 76 kHz signal crosses zero.This prevents spurious frequency components from being generated andinterfering with other signals in the pass band of the transmitter. Inthe preferred embodiment, only the ASK modulator 760 is utilized.

The MCU 764 is operable to control the limiters 712 and also to controla sub-base enhancement limiter 770. The limiter 770 is disposed suchthat it receives on the input thereof the output of a crossover circuit772, which has the input thereof connected to the output of a summingjunction 774. The summing junction 774 is operable to sum the output ofa left channel amplifier 776 and a right channel amplifier 778. Theoutput of the limiter 770 is input to a summing junction 780, which sumsthe output of the limiter 770 with the output of a sub-base amplifier782 for receiving a sub-base signal. The output of the summing junction780 provides a sub-base enhancement signal. In general, the sub-baseenhancement is due to the fact that the receiver low end frequencyresponse is limited to approximately 300 Hz due to the volumetricconsiderations of the loudspeaker enclosure. By utilizing supplementallow frequency speakers, the overall system low frequency response can beextended. This is an output that goes to an external speaker via aconnector 784.

The MCU 764 is operable to operate as either a master or a slave. In themaster mode, the MCU 764 generates the sync signal and transmits it viaan output 788 to the other systems. The volume controls are received onan input 790 and a mode control input is received on line 792. A basicserial connector 794 is provided for allowing interface external to thesystem.

In certain situations, it may be desirable to sum one of the channels,the PSE1 channel, with the other channels such that, for example,background material on a single channel can be summed with the otherchannels. This is facilitated by disposing summing junctions 800 and 802in the left and right channel paths of each of the PSE2, PSE3 and PSE4channels. The output of the left amplifier 694 for the left channel onPSE1 is selectively connected to summing junctions 800 via a switch 804and the output of the amplifier 696 for the PSE1 channel is selectivelyconnected to the second input of the summing junction 802 via a switch806.

Referring now to FIG. 16, there is illustrated an alternate embodimentfor a configuration for the transmitters and zones. In the embodiment ofFIG. 16, there are illustrated a plurality of transmitters 810, eachhaving a Zone 812 associated therewith. Each of the Zones 812 aredisposed adjacent to each other and slightly overlapping. As describedabove, the overlapping zones cannot have common channels, such that onezone may have channel 1 and 2 and an adjacent zone may have channel 3and 4. This provides the user the ability to walk from zone to zone andreceive different programming, as described hereinabove.

In the embodiment of FIG. 16, an additional set of flood transmitters814 are provided, the flood transmitters 814 acting as one transmittersuch that they all operate on the same sync frequency with the samecommand transmitted. Typically, they will be configured such that theycover the entire area, including all of the area within which thetransmitters 810 are disposed and operate at the lowest sync frequency.For example, the sync frequency of the flood transmitters 814 will be 12Hz, whereas the transmitters 810 will be alternately disposed at a syncfrequency of 16 Hz and 24 Hz. Additionally, the flood transmitters willoperate such that they are on the lowest channel with the lowest pulsewidth. If they were at a mute pulse width, this would be 1 ms. Thereason for this is that when a user goes from the lowest sync rate to ahigher sync rate, the additional pulse in the, for example, 24 Hz syncrate zone will register as a higher sync rate and the pulse width of the24 Hz zone, being larger than the 12 Hz zone, will override the pulsewidth of the 12 Hz flood zone. Therefore, as soon as the extra pulse isdetected, the wide pulse width will be detected for all pulses and theuser's receiver will immediately and seamlessly detect that it is withinone of the zones 812. In this manner, the user will always be subjectedto some type of background music or to a mute signal when leaving anyZone 812 and entering the flood zone. Although the Zones 812 are shownas overlapping, they could be spread throughout an exhibit hall, withthe remaining portion of the exhibit hall subjected to the 12 Hz syncrate and the command associated therewith.

In summary, there has been disclosed a method and apparatus for allowingcommunication in adjacent zones such that a user wearing (or carrying) aheadset can traverse from zone to zone and communicate with that zonemerely by entering the zone itself. All zones are synchronized to acommon sync rate with the discriminating aspect for the receivers fortransferring from one zone to another being a change in sync rates.Commands are transmitted at the sync rate by pulse width modulating thepulses associated with the sync signal. By associating commands withincrementally different pulse widths and sync rates, these commands canbe transmitted at the same time as the sync signal is transmitted. Thesecommands, once received, indicate the channel that is being transmittedand the channel to which the receiver is to be tuned.

Although the present embodiment has been described in detail, it shouldbe understood that various changes, substitutions and alterations can bemade therein without departing from the spirit and scope of theinvention as defined by the appended claims.

What is claimed is:
 1. A method for communicating with mobile receiversin different zones, comprising the steps of:providing first programinformation associated with a first zone; providing second programinformation associated with a second zone, said first and second programinformation relating to different programs; transmitting first commandinformation from a first transmitter in the first zone over a commoncommand link within the first zone, the first command informationcontaining configuration information related to the first programinformation and priority information defining the first transmitter ashaving the highest priority; transmitting second command informationfrom a second transmitter in the second zone over the common commandlink within the second zone, the second command information containingconfiguration information related to the second program information andpriority information defining the second transmitter as having a lowerpriority than the first transmitter, wherein the step of transmittingthe first command information and the step of transmitting the secondcommand information can occur simultaneously; receiving at the mobilereceiver the command information from the common command link associatedwith the one of the first and second zones in which the mobile receiverresides and configuring the mobile receiver in accordance with thehighest priority one of the received first and second commandinformation received over the common command link, which received firstand second command information can be received simultaneously; andreproducing at the mobile receiver the first or second programinformation in accordance with the configuration information and fromthe one of the first and second transmitters having the highestpriority.
 2. The method of claim 1, wherein:the step of providing firstprogram information comprises the step of transmitting the first programinformation in the first zone on first program channels over a firstcommunication link from the first transmitter located in the first zone;the step of providing second program information comprises the step oftransmitting the second program information in the second zone on secondprogram channels over a second communication link from the secondtransmitter located in the second zone; and the step of reproducingcomprising receiving at the mobile receiver the first or second programinformation on the associated first or second program channels over theassociated one of said first and second communication links inaccordance with the configuration information and from the one of thefirst and second transmitters having the highest priority.
 3. The methodof claim 2, wherein the first and second zones partially overlap, suchthat in the overlapping portion of the first and second zones, themobile receiver can receive commands from both the first and secondtransmitters over the common command link.
 4. The method of claim 3 andfurther comprising the steps of:transmitting third program informationin a third zone on a third program channel over a third communicationlink from a third transmitter located in said third zone; transmittingthird command information from the third transmitter in the third zoneover the common command link within the third zone, the third commandinformation containing configuration information related to the thirdprogram information and priority information defining the thirdtransmitter as having a higher priority than the second transmitter; andthe step of receiving at the mobile receiver further comprisingreceiving at the mobile receiver the command information from the commoncommand link and configuring the mobile receiver in accordance with thehighest priority of the received one of the first, second and thirdcommand information.
 5. The method of claim 4, wherein the first andthird zones do not overlap, with the second zone overlapping the firstand third zones.
 6. The method of claim 5, wherein the first programchannels can be identical to the third program channel.
 7. The method ofclaim 2, wherein the step of transmitting the first program informationand the step of transmitting the second program information comprisescontinuously transmitting either the first program information from thefirst transmitter or the second program information from the secondtransmitter.
 8. The method of claim 2, wherein the first and secondcommand information are synchronized.
 9. The method of claim 1, whereinthe first program information and the second program informationcomprise audio programs and the step of reproducing at the mobilereceiver comprises converting the audio program to an audio output for auser for output from headphones that are worn by the user, and themobile receiver comprises a headset.
 10. The method of claim 2, whereinthe first and second program information comprise audio programinformation.
 11. The method of claim 10, wherein the second programinformation comprises mute information and the step of reproducing isinhibited when the mobile receiver is in the second zone and receivingonly said second command information.
 12. The method of claim 2, whereinthe step of transmitting first command information and second commandinformation comprises transmitting common information over both saidfirst and second transmitters.
 13. The method of claim 2, wherein thestep of transmitting first and second command information comprisestransmitting a self-test command from either said first transmitter orsaid second transmitter and, upon receiving the self-test command,performing a predetermined self-test procedure on the mobile receiverreceiving the self-test command.
 14. The method of claim 2, wherein thefirst program channels comprise a plurality of distinct first programchannels and the first communication link provides a plurality ofdistinct first communication links each associated with one of thedistinct first program channels, and the second program channelsproviding a plurality of distinct second program channels and the secondcommunication link providing a plurality of distinct secondcommunication links with each of the distinct communication linksassociated with one of the distinct communication links associated withone of the distinct second program channels, the first commandinformation operable to define the one of the distinct first programchannels that is to be received by the mobile receiver and the secondcommand information operable to define the one of the second distinctprogram channels to be received by the mobile receiver.
 15. The methodof claim 14 and further comprising the step of overriding the commandinformation and preselecting at the mobile receiver the one of the firstand second distinct program channels to be received.
 16. A system forcommunicating with mobile receivers in different zones, comprising:afirst zone having first program information associated therewith; asecond zone having second program information associated therewith; afirst transmitter for transmitting first command information in saidfirst zone over a common command link, said first command informationcontaining configuration information related to said first programinformation and priority information defining said first transmitter ashaving the highest priority; a second transmitter for transmittingsecond command information within said second zone over said commoncommand link, said second command information containing configurationinformation related to said second program information and priorityinformation defining said second transmitter as having a lower prioritythan said first transmitter; a receiver associated with the mobilereceiver for receiving said command information from said common commandlink associated with the one of said first and second zones in which themobile receiver resides and configuring the mobile receiver inaccordance with the highest priority one of the received first andsecond command information received over said common command link; andan audio system for reproducing at the mobile receiver said first orsecond programmed information in accordance with said configurationinformation and from the one of said first and second transmittershaving the highest priority.